Liquid fuel burner system with spray nozzle evacuator



Aug. 17, 1954 Q D, MacCRACKEN ETAL v 2,686,562

LIQUID FUEL BURNER SYSTEM WITH SPRAY NOZZLE EVACUATOR Filed Jan. 20, 1950 2 Sheets-Sheet l A TTORNEYS Aug- 17, 1954 c. D. MaCcRAcKEN ETAL 2,686,562

LIQUID FUEL BURNER SYSTEM WITH SPRAY NOZZLE EVACUATOR Filed Jan. 20, 1950 2 Sheets-Sheet 2 :Fig/,4.

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M1 n? Af. www BY Patented Aug. 17, 1954 UNITED STATES LIQUID FUEL BURNER SYSTEM WITH SPRAY NOZZLE EVACUATOR Calvin D. MacCracken, Tenafly, N. J., and George N. Miles, Orangeburg, N. Y., assignors to Jet- Heet, Inc., Englewood, N. J., a corporation of New York f Application January 20, 1950, Serial No. 139,778

2 Claims. l

This invention relates to liquid fuel burning systems and more particularly to such systems containing means for withdrawing fuel from the spray nozzle and adjacent fuel lines when the fuel burner is shut olf.

In pressure atomizing spray-type oil burners such as those used for heating systems and in other liquid fuel burning systems, the oil or other liquid fuel is delivered under pressure to a spray nozzle constituting a part of the burner. Various devices in the nature of shut-off valves have heretofore been utilized to close the supply line to the nozzle when the pressure drops below a certain point with resulting extinction of the flame. This, however, leaves the nozzle full of fuel at the time of shut-off and this fuel, standing in the nozzle, may be expanded by heat radiated from hot bodies surrounding the nozzle with the result that a small quantity of fuel may drip from the nozzle onto hot parts of the burner, causing smoky conditions following shut-olf. In heating systems particularly this is disadvantageous as offensive odors may be disseminated through the building and soot will be deposited on heat exchange surfaces reducing heat transfer eiiiciency. Smoky shut-olf may also be caused by imperfect or worn-off valves or by an air pocket trapped under pressure in the fuel supply line which air pocket, when the pressure is released and the shut-off valve is closed, acts as an accumulator to continue pumping oil out of the nozzle. This eifect is often caused by a pressure gauge in the pressure line. Furthermore, in many types of installations the nozzle is subjected to a substantial quantity of radiated heat with the result that the stagnant oil or other fuel carbonizes or becomes gummy on the surfaces of the nozzle parts and is likely to clog the small apertures of the nozzle.

The object of the present invention is to provide a solution of these problems and comprises apparatus, which operates automatically, when the fuel pressure to the nozzle is shut off or ren leased, to Withdraw the oil from the nozzle and preferably also from at least portions of the fuel lines leading thereto, at the same time sucking air in through the line orices in the spray nozzle with a rapid rate of ow so that these orifices are left substantially clean. It also acts to seal off the nozzle from the source of fuel supply, preventing leakage of the fuel to the nozzle. When the fuel burner is again started up the apparatus operates to refill promptly the nozzle and the fuel lines leading thereto and to reopen the fuel supply line to the nozzle.

The invention will best be understood by refer- (Cl. 15S-36.3)

ence to the following detailed description of the present preferred embodiments of the invention, taken in conjunction with the drawings, in which:

Fig. l is a central cross-sectional elevation through the fuel pressure actuated energy-storing and scavenging device;

Fig. 2 is a schematic diagram of a fuel burning system in which the spray nozzle is of the returnflow type having fuel supply and fuel return lines connected thereto and in which pressure regulating valves are associated with the pump and fuel return lines;

Fig, 3 is a diagram of a system similar to that shown in Fig. 2 with the addition of an oil pressure release valve and a pressure gauge in the fuel return line; and

Fig. 4 is an elevation of part of the system showing a preferred arrangement of the fuel nozzle and scavenging device.

Referring to Fig. l, the scavenging device, which is generally in the nature of an accumulator or energy-storing device, having certain novel features, is composed of a body le containing a cylinder il provided at its inlet end with a head l2 secured to the body by means of screws I4, a circular gasket i5 being interposed between these parts to form a fluid-tight seal. Extending outwardly of the other end of the cylinder is a spring chamber it terminating in a small orifice I8 above which the head of body l@ is provided with interconnecting holes communicating with the orice, drilled and tapped as shown at E9, 26 and 2l to receive pipe fittings or the like. The head l2 is preferably provided with a boss 22 which is likewise drilled and tapped as shown at 24 to receive a fuel supply pipe 25. Slidably mounted in the cylinder El is a piston 26 externally grooved as shown at 2li and 29 so that its outer surface is composed of the upper flange 3Q, the middle flange 3! and the lower flange 32. In groove 28, between the flanges 39 and 3i, the piston is provided with a iiuid seal in the form of an O-ring 33, the groove 23 being so dimensioned as to slightly compress the O-ring radially between the piston and the cylinder wall while providing room for slight axial movement within the groove. The operation of this type of seal to provide a fluid-tight joint between relatively ymovable parts is well known. The central portion of the piston is provided with a cup 34 which serves to retain one end of a compression spring 35 contained within the chamber it and of such length as to be under some compression when the piston is resting against head E2. The cylinder Il is provided in its side wall with an outlet port 36 which is so positioned that it is cleared by the flange 3l when the piston 26 is at the upper end of the cylinder as shown in the drawing. The flange 32 is provided merely to give the piston stability in the cylinder and to permit the now of fuel to the outlet port 36. This flange is provided with a pluraltiy of holes permitting a free flow of fluid into the groove 29. The oonduit which delivers the fuel under pressure to the spray nozzle of the fuel burner is shown at 39 as screwed into the tapped hole 4i! which communicates with port 36.

In Figs. 2 and 3 the fuel supply tank is shown at 4 l, connected by a pipe l2 to the fuel pump ed, the delivery side of which is connected to the pipe 25 which leads to the accumulator device just described. The conduit 3S leads therefrom to the spray nozzle 45.

Referring to Figs. 1 and 2, the operation of the apparatus contained in the system shown in Fig. 2 is as follows: When the pump lilis started, at which time there is no pressure in conduit 25, the piston 2li is at the lower end of the cylinder resting against head l2 as shown in dotted lines in Fig. l. As the pump delivers fuel under pressure the pressure of the fuel acts to move piston 25, compressing the spring 35 until such time as the O-ring 33 passes outlet port B, when the fuel is free to flow into the conduit 39 to nozzle Q5. When the pump stops and the pressure in conduit 25 drops below the point where it can hold the spring 35 under compression, the piston will move in the cylinder toward the head l2. After the -ring 33 passes the outlet port 3S, all further movement of the piston will create suction in conduit 39 and draw fuel from the nozzle l5 as fast as air is able to enter the nozzle through its spray orifice, which is of very small size. The eective capacityof cylinder il is made suiiicient to completely empty the nozzle (i. e., the fuel conducting spaces therein) and preferabiy also at least part ofv conduit 39. More specifically, the volume of the cylinder H, and the distance between the port 36 and the head l2, should be such as to provide within the cylinder and between the port 36 and the head i2 a volume at least as great as that of the fuel conducting spaces inside the nozzle l5 plus the volume displaced by the piston 2t. The initial movement of the piston keeps the fuel flowing through port 3S under pressure until the instant when that port is sealed by O-ring 33,

giving a sharp cut-off which is followed immediately by a reversal of flow so that no drip from the nozzle can occur. In this system it is essential that there be no check valve in the supply lines which would maintain pressure in cylinder H after the pump is shut olf and it is also assumed that a slight reverse flow through the pump is possible. Since the nozzle shown in Fig. 2 is of the return-flow type, a portion of the oil delivered to the nozzle is permitted to return from it, without being forced through the spray orifice, through a pressure regulator Eil connected with the nozzle through conduits l, `$32 both of which are connected to the head of the accumulator, as at the openings iii and for example. Oil passing through the pressure regulator 53 is returned to the fuel supply tank 4l through conduit 54. For further details of a suitable pressure regulator reference may be had to the copending application Ser. No. 70,773, filed Jan. 13, 1949 by Calvin D. MacCracken and Charles W. Wood, assigned to the assignee of the present application, and now Patent No. 2,590,111 issued March 25, 1952, which also describes in more detail the operation of a return-dow system.

Fig. 3 shows a system which is like that shown in Fig. 2 except that a pressure relief valve 55 is connected between the pressure line 25 and the return line 54. This valve may be of the well known solenoid operated type which is under the control of a thermostat which causes the valve to open and provide a by-pass for the oil delivered by the pump when heat is no longer desired, even though the pump continues to run. The opening of this relief valve will of course completely relieve the pressure in cylinder ll so that the piston 26 will move in response to the energy stored in spring 35 and suck oil from the nozzle 45 and the lines leading thereto.

In the systems of both Fig. 2 and Fig. 3, a. pressure regulating valve 56 is shown which may be used to control the pressure of the oil in conduit 25. Such regulating valves are a common feature in fuel burning systems and their operation is well understood. They are frequently incorporated in the pump unit as an integral part thereof.

In Fig, 3 a pressure gauge 58 is shown which may be inserted in the system by connection with the accumulator at the tapped hole 2l. Thus the head of body i9 provides a convenient means for interconnecting the fuel return line from the nozzle, the line to the pressure regulator 50, the scavenging device and a pressure gauge.

The outlet port 3 6 and the orifice i8 which communicates with the tapped holes i9, 2e and 2l preferably have restricted cross-sectional areas and are preferably of substantially the same size so that when the piston 25 moves toward the head i2 fuel will be drawn at about equal rates through the pipes 39 and 5 l. It has been found that small holes about L inch in diameter are satisfactory.

Referring to Fig. 4, the installation of the above described apparatus is preferably made with the scavenging device placed below the level of the nozzle i5 and the conduits connecting these two parts are preferably small diameter tubing so that their fluidcapacity is not great. When the pressure has been relieved in the feed line 25 and the scavenging device has operated, the liquid in pipes 39 and 5l, if any remains, will seek a common level because they are in communication through the scavenging device at this time. This is indicated in Fig. e by the broken line marked liquid level on the assumption that not all of the liquid in the lines 39 and 5i has been drawn into the scavenging device. It will thus be seen that mounting the nozzle with the feed and return flow lines extending downwardlyv therefrom assures that no oil will flow by gravity to the nozzle after it has been drained. It will also be noted that piston 26, in the position it assumes when not subject to the pressure of oil supplied by the pump, acts as a shut-off valve preventing the liow of oil from the fuel tank to the nozzle by gravity in the event that the fuel tank is at a higher level than the nozzle.

While the invention has been explained by reference to the details of particular embodiments, they are to be considered to be merely illustrative of the invention which is hereinafter defined in the claims.

What is claimed is:

l. In a liquid fuel burner system having a spray nozzle of the return flow type, a pump for supplying fuel under pressure to said nozzle, a fuel feed line connected to said nozzle, a fuel return line connected to said nozzle, a cylinder communicating at one end with said pump to receive oil under pressure, a piston operating in said cylinder, a compression spring of such strength as to be compressible by the pressure of said fuel, said spring acting on said piston to move the piston toward said one end, a first port in the wall of said cylinder intermediate its ends at a point remote from said one end and communicating with said fuel feed line, and a second port opening into said cylinder` at a point beyond-the maximum spring-compressing travel of the piston and communicating with said fuel return line, the dimensions of said cylinder and the location of said rst port being such as to provide, within said cylinder and between said first port and said one end, a volume at least as great as that of the fuel conducting spaces inside said nozzle plus the volume displaced by said piston, whereby under the pressure of fuel from said pump said piston moves beyond said first-mentioned port to permit fuel to flow to the nozzle and on the release of said pressure moves.

back pastv said rst-mentionedrport through a substantial distance to suck fuel from both said fuel feed and fuel return lines.

2. In a liquid fuel burner system having a spray nozzle of the return flow type, a pump for supplying fuel 4under pressure to said nozzle, a fuel feed line connected to said nozzle, a fuel return line connected to said nozzle, a cylinder communicating at one end with said pump to receve oil under pressure, a piston operating in said cylinder, a compression spring of such strength as to be compressible by the pressure of said fuel, said spring acting on said piston to move the piston toward said one end, a first port in the Wall of said cylinder intermediate its ends at a point remote from said one end and communicating with said fuel feed line, and a second port opening into said cylinder at a point beyond the maximum spring-compressing travel of the piston and communicating with said fuel return line, said ports being restricted in size and of substantially the same size, the dimensions of said cylinder and the location of said first port being such as to provide, Within said cylinder and between said first port and said one end, a volume at least as great as that of the fuel conducting spaces inside said nozzle plus the volume displaced by said piston, whereby under the pressure of fuel from said pump said piston moves beyond said first-mentioned port to permit fuel to iiow to the nozzle and on the release of said pressure moves back past said first-mentioned port through a substantial distance to suck fuel from both said fuel feed and fuel return lines at substantially the same rate.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,858,302 Marshall May 17, 1932 2,248,395 Taper et al. July 8, 1941 2,468,960 Case May 3, 1949 2,494,778 Plass Jan. 17, 1950 2,592,132 Feiden et al. Apr. 8, 1952 FOREIGN PATENTS Number Country Date 326,388 Great Britain Mar. 13, 1930 918,129 France Oct. 7, 1946 

